GEL2 Exam 2 (part 2)

Continental Drift is a unifying theory that explains Earth's topography and integrates our understanding of rock formation, mountain building, and terrain modification.

False

Cratons are isostatically instable.

False

Earth's diameter is increasing significantly due to the generation of new ocean crust.

False

In seafloor convergence, oceanic crust splits and moves away from spreading ridges.

False

Modern continental shorelines coincide exactly with the edges of the original oceanic rift.

False

Oceanic crust is geologically old and preserves a long record of geologic activity.

False

Passive continental margins coincide with the geologically active edges of tectonic plates.

False

The driving force for lithospheric plate motion is conduction in the mantle.

False

When a plate capped by continental crust converges with a plate capped by oceanic crust, the continental plate will undergo subduction.

False

__________ has influenced virtually every part of the Earth system over the history of planet Earth.

Plate tectonics

__________ gravity anomalies result from concentrations of high-density rock under the surface.

Positive

An __________ marks the place where oceanic-capped lithosphere sinks into the asthenosphere.

oceanic trench

The Atlantic Ocean margins of the Americas, Africa, and Europe are examples of __________ continental margins.

passive

Gases from __________ continue to play an important role in the climate and the long-term composition of the atmosphere.

volcanoes

___________ plate margins are fractures in the lithosphere where two plates slide past each other.

Transform fault

As the plates of a transform fault grind past one another their edges may grab and lock, forcing the rocks on both sides to flex and bend.

True

Divergent plate margins start in continents and become oceans.

True

Earth's climatic zones and the distribution of plant and animal communities are fundamentally affected by the presence of modern orogens.

True

If plate tectonics operated early in Earth history, it is likely that the plates were small, rapidly moving, and constantly recycled back into the mantle.

True

Large mountain ranges are characterized by significant negative gravity anomalies because of their deep, low-density roots.

True

Measuring the speed and direction of movement of lithospheric plates requires a fixed frame of reference, such as distant stars.

True

Since Pangaea, the lithosphere has broken into nine major plates and a large number of smaller plates.

True

Studies of rock paleomagnetism have revealed the ancient positions of Earth's magnetic poles.

True

Subduction zones are marked by deep trenches where ocean-capped lithosphere sinks into the asthenosphere.

True

When both plates of a converging pair are capped by low-density continental crust, neither plate will undergo subduction.

True

When two plates capped by dense oceanic crust converge, one of the plates will subduct beneath the other plate.

True

A typical rate of seafloor spreading along the Mid-Atlantic Ridge is a) 2 to 4 cm/year. b) 2 to 4 feet/year. c) 2 to 4 inches/year. d) 2 to 4 meters/year.

a) 2 to 4 cm/year.

What type of plate margin is the majority of the rim surrounding the Pacific Ocean? a) Active. b) Passive.

a) Active.

What type of plate boundary created Japan? a) Convergent. b) Divergent. c) Transform.

a) Convergent.

What type of plate boundary created the Andes Mountains? a) Convergent. b) Divergent. c) Transform.

a) Convergent.

About how old is the oldest craton within the North American continental shield? a) Greater than 2.5 billion years old. b) About 2 billion years old. c) About 1 billion years old. d) Less than 1 billion years old.

a) Greater than 2.5 billion years old.

What does the flotation height of an object depend upon? a) Mass and volume. b) Mass and density. c) Volume and density. d) Size and shape.

b) Mass and density.

Where are the youngest seafloor rocks found? a) Nearest the continental margins. b) Nearest the rift valleys of the mid-ocean ridges. c) Within the deep sea trenches. d) Evenly distributed over the ocean basins.

b) Nearest the rift valleys of the mid-ocean ridges.

Assume there is a mountain range with a deep root of low-density continental rock extending into the underlying asthenosphere. Would this produce a negative or positive gravity anomaly? a) Positive. b) Negative. c) Need more information to answer this question.

b) Negative.

Subduction zones can generally lead to a) Deep trenches. b) Island arcs. c) Mountain ranges. d) Any of these.

d) Any of these.

The mesosaurus is an extinct reptile who lived over 200 million years ago. Its fossil remains have been found in Southern Africa and Eastern South America, but nowhere else. Today, we know that these two regions of the Earth are vastly different in terms of climatology, flora, and fauna. How does the discovery of the mesosaurus fossil support the concept of Continental Drift (and subsequently Plate Tectonics)? a) Mesosaurus was a coastal animal and therefore could not have crossed the Atlantic Ocean. The distribution of the mesosaurus fossils indicate that the two continents used to be joined together. b) It really doesn't. The mesosaurus was a good swimmer and most likely swam the expanse of the Atlantic Ocean. c) The distribution of the mesosaurus indicates that the fauna of Southern Africa and Eastern South America used to be the same, but nothing else.

a) Mesosaurus was a coastal animal and therefore could not have crossed the Atlantic Ocean. The distribution of the mesosaurus fossils indicate that the two continents used to be joined together.

How does plate tectonics influence the composition of ocean water? a) Submarine volcanoes along mid-ocean ridges lead to chemical reactions between the ocean water and the hot rocks of the seafloor. b) Material from the core seeps into the ocean via submarine volcanoes. c) Oceanic trenches from subduction zones trap salts and minerals thereby changing the overall ocean water composition. d) None of these.

a) Submarine volcanoes along mid-ocean ridges lead to chemical reactions between the ocean water and the hot rocks of the seafloor.

What is the Benioff Zone? a) The contact zone where one slab of lithosphere subducts beneath another slab of lithosphere. b) The contact zone where one slab of lithosphere diverges from another slab of lithosphere. c) The contact zone where one slab of lithosphere moves adjacent to another slab of lithosphere. d) The oceanic zone where hydrothermal vents exist.

a) The contact zone where one slab of lithosphere subducts beneath another slab of lithosphere.

Of the following, which can be used to determine the absolute motion of plates? a) Volcanic hot spots (such as the Hawaiian Island chain). b) Magnetic reversals chronicled in the oceanic crust. c) Sediment thickness along continental margins. d) The position of Australia relative to the other continents.

a) Volcanic hot spots (such as the Hawaiian Island chain).

Large, flat areas known as __________ are a major topographic feature of the seafloor.

abyssal plains

The break-up of Pangaea to form our modern-day continents started about how long ago? a) 100 million years ago. b) 200 million years ago. c) 300 million years ago. d) 50 million years ago.

b) 200 million years ago.

An assemblage of cratons and orogens is called a a) Continent. b) Continental shield. c) Ocean basin. d) Subduction zone.

b) Continental shield.

The volcanic mountain range of the Andes is defined as a a) Volcanic island arc. b) Continental volcanic arc. c) Himalaya-like mountain zone. d) Mini-supercontinent.

b) Continental volcanic arc.

Along what type of plate boundary does subduction occur? a) Divergent. b) Convergent. c) Transform.

b) Convergent.

Along what type of plate boundary does sea-floor spreading occur? a) Convergent. b) Divergent. c) Transform.

b) Divergent.

What type of plate boundary created Iceland? a) Convergent. b) Divergent. c) Transform.

b) Divergent.

What was the first evidence that lead Alfred Wegener to suspect the continents were once connected? a) The clock-like ebb and flow of the tides. b) The continents simply looked like they fit together, especially Africa and South America. c) The direction that the currents moved. d) Alfred Wegener discovered marine sediments in the Himalaya Mountains.

b) The continents simply looked like they fit together, especially Africa and South America.

What is a subduction zone? a) Where a continental plate breaks and diverges. b) Where one lithospheric plate is dragged or pushed below another lithospheric plate. c) Where one lithospheric plate slides past another lithospheric plate. d) None of the above

b) Where one lithospheric plate is dragged or pushed below another lithospheric plate.

Why are the continents about 20 times older than the oldest ocean basins? a) Because ocean basins form from spreading centers, which produces new oceanic crust. b) Because continental material is low-density and does not get thrust into the subduction zone. c) Both of these are true

c) Both of these are true

What type of plate boundary created the Himalaya Mountains? a) Transform. b) Divergent. c) Convergent.

c) Convergent.

The Earth's oldest rocks are found a) In the abyssal plains. b) On volcanic islands like Hawaii. c) In the cores of continents. d) At the mid-ocean ridges.

c) In the cores of continents.

Where is active sea-floor spreading occurring today? a) Lake Michigan b) The Great Salt Lake. c) The Red Sea. d) The Mississippi River.

c) The Red Sea.

What type of plate boundary is associated with the San Andreas Fault in California? a) Divergent. b) Convergent. c) Transform.

c) Transform.

A __________ is a stable core of very ancient rock.

craton

How do hot spots and plate tectonics account for the islands of the Hawaiian Island chain varying in age? a) The volcanic hot spot in the middle of the Pacific Ocean was originally in the Atlantic Ocean and is therefore quite old. b) Hot spots and plate tectonics cannot account for the age variability. c) The volcanic hot spot in the middle of the Pacific Ocean is due to the divergence of the East Pacific Rise. d) As molten material continually seeped from the hot spot, an island(s) would form. As the Pacific Plate continued to move the island locked to the Pacific Plate would move as well. A new island would then form above the hot spot.

d) As molten material continually seeped from the hot spot, an island(s) would form. As the Pacific Plate continued to move the island locked to the Pacific Plate would move as well. A new island would then form above the hot spot.

Which of the following statements is true for the asthenosphere? a) The material that makes up the Himalaya Mountains. b) A brittle layer of crust plus upper mantle. c) The origination point for Earth's internal convection of energy. d) Zone in the upper mantle that is a solid but capable of flowing like a liquid.

d) Zone in the upper mantle that is a solid but capable of flowing like a liquid.

About how old are the oldest known rocks on Earth? a) 4.56 billion years old. b) 2.98 billion years old. c) 3.51 billion years old. d) 2.57 billion years old. e) 4.28 billion years old.

e) 4.28 billion years old.

The lithosphere behaves as is it were __________ on the asthenosphere.

floating